In Morocco—especially around the fossil world of Erfoud—you’ll hear the word “ammonite” used for many spiral shell fossils. But in paleontology, the story is more specific. Many spirals people call “ammonites” in the Devonian context are actually ammonoids with goniatitic sutures—often referred to as goniatites in the fossil trade.
This post clears up the names without making it complicated, and shows you the one feature that matters most when you want to tell a goniatite from an ammonite.

What are ammonites and goniatites?

Both are part of the same bigger group:
  • Class: Cephalopoda
  • Subclass: Ammonoidea
So yes—they’re closely related. Think “ammonoids” as the big family of extinct spiral-shelled cephalopods.
Where people get confused is the naming:

  • “Goniatite” is often used for ammonoids with a goniatitic suture pattern (common in Paleozoic rocks, including Devonian).
  • “Ammonite” is often used casually to mean “any ammonoid,” but in strict paleontology “true ammonites” usually refers to later ammonoid groups with more complex sutures.

When did they live?

Ammonoidea lived for a very long time in Earth’s history. In Morocco, many spiral fossils people see around Erfoud are associated with Paleozoic marine rocks, including Devonian layers. That’s why you’ll often see Devonian spirals discussed and sold under names like “goniatite” and sometimes “ammonite” in shops.

The one feature that tells you what you have: sutures

To identify these fossils, you don’t start with the spiral shape. You start with sutures.
Sutures are the lines formed where the internal shell walls (septa) meet the outer shell. On a fossil, sutures can look like a pattern of wavy lines—sometimes visible on the outer surface, and very clear when a fossil is cut/polished or naturally broken.
Goniatitic sutures (often called “goniatites”)

  • Relatively simple, rounded wave-like pattern
  • Clean and repeating, not “frilly” or extremely complex
Ammonitic sutures (often called “ammonites”)

  • Very complex, highly frilled, “leafy” or intricate patterns
  • Dense complexity—like a detailed lace edge
If you remember only one thing:

  • Simple sutures = goniatite-type
  • Very complex sutures = ammonite-type

Why Morocco (and Erfoud) is famous for ammonoids

Morocco is special because fossil layers are well-exposed in desert environments, and because the region has strong traditions of fossil preparation.
Erfoud is often mentioned because it’s a hub where fossils are prepared, identified, and presented. Many travelers visiting Merzouga pass through or near Erfoud, and the fossil culture is very visible—workshops, displays, and lots of local knowledge.